Several Methods of Measuring Wind Speed and Direction
Wind speed refers to the distance that the wind flows in unit time; wind force refers to the force of the wind when it blows on the object. There are no grades for wind speed, but there are grades for wind power, and wind speed is the basis for the division of wind power grades. Generally speaking, the greater the wind speed and the higher the wind level, the greater the destructive power of the wind.
1. Why should we emphasize the measurement of wind speed and wind force?
Wind force and wind speed are important indexes in meteorological research, and they are also the key elements that people pay attention to. It not only has a great impact on people's daily activities, but also has great significance for meteorological research, navigation and other work, so measuring the wind speed and direction in advance is conducive to the smooth development of various activities.
2. What are the methods for measuring wind speed and wind direction?
According to the measurement principle, we will introduce the following types of methods: traditional measurement, mechanical method, ultrasonic method, and calorimetric method.
traditional measurement
1. Wind direction measurement: use wind vane
The direction of the wind direction arrow on the wind vane indicates which direction the wind is blowing at that time. When there is a certain angle between the wind vane and the direction of the airflow, the airflow will generate a pressure on the tail of the wind vane. Its size is proportional to the projection of the geometric shape of the wind vane on the vertical plane of the airflow direction. The wind vane head has a small windward area and the tail wing has a large windward area. The wind pressure generated by this pressure difference makes the wind vane rotate around the vertical axis until the wind vane is in contact with the airflow. parallel. The wind direction can be easily observed from the relative position between the wind vane and the fixed main azimuth indicating pole.
2. Wind speed measurement: use an anemometer
There is a rectangular wind pressure plate on the wind detector, and an arc-shaped frame is installed beside the wind pressure plate, and there are long and short teeth on the frame. The number of long and short teeth raised by the wind pressure plate indicates the magnitude of the wind force, and the greater the wind force, the higher the wind speed level.
mechanical wind measurement
Mechanical wind measurement, such as wind meter wind measurement, looks like a mechanical watch, and is generally used to measure the wind in shafts. It is necessary to estimate the wind speed first, then use the wind gauge and stopwatch to reset the pointer of the wind gauge and the stopwatch to zero, and then make the wind gauge face the wind flow and be perpendicular to the direction of the wind flow. After the wind gauge idles for 30 seconds, turn on the switch of the wind gauge and the stopwatch at the same time to start the measurement . It should be noted that the wind measurement at the same section shall not be less than 3 times, and the wind measurement shall run smoothly during the wind measurement process. For example, the wind speed and direction sensor adopts a typical mechanical wind measurement method, which makes better use of wind energy and supports the development of new energy wind power generation technology.
Ultrasonic Velocimetry
The working principle of ultrasonic wind measurement is to use the ultrasonic time difference method to realize the measurement of wind speed and direction. Due to the propagation speed of sound in the air, it will superimpose with the airflow speed in the wind direction. If the ultrasonic wave travels in the same direction as the wind, its speed will increase; conversely, if the ultrasonic wave travels in the opposite direction to the wind, its speed will slow down. Therefore, under fixed detection conditions, the speed of ultrasonic waves propagating in the air can correspond to the wind speed function. Accurate wind speed and wind direction can be obtained through calculation.
calorimetric principle measurement method
A typical example of using the calorimetric principle to measure wind speed is the anemometer. Its basic principle is to place a thin metal wire in the fluid, and heat the wire through an electric current to make its temperature higher than the temperature of the fluid. Therefore, the wind speed of the wire is referred to as the "Hotline". When the fluid flows through the wire in the vertical direction, it will take away part of the heat of the wire and reduce the temperature of the wire. According to the theory of forced convection heat exchange, there is a relationship between the heat Q lost by the hot line and the velocity v of the fluid. The anemometer is an instrument capable of measuring low wind speeds. It consists of two parts: a hot-ball rod probe and a measuring instrument. The probe has a glass bulb with a nichrome wire coil and two thermocouples wound inside the bulb. The cold junction of the thermocouple is attached to a phosphor-bronze post exposed directly to the air flow. When a certain amount of current passes through the heating ring, the temperature of the glass bulb rises. The degree of increase is related to the wind speed, and the degree of increase is large when the wind speed is small; otherwise, the degree of increase is small. The magnitude of the rise is indicated on the meter by means of a thermocouple. According to the reading of the electric meter, check the calibration curve to find out the wind speed at that time.
